Solid peroxide stimulated phenanthrene removal from contaminated river sediment

Katherine Stuart Schaffnit

While extensive data are available regarding polycyclic aromatic hydrocarbon (PAH) contamination in soils, far fewer studies have been dedicated to PAH contaminated sediments. Because current treatment options for PAH contaminated sediments are expensive and invasive, bioremediation provides a more cost effective treatment strategy. A variety of naturally occurring soil bacteria are capable of degrading PAHs either through metabolism or cometabolism (Ri-He, Ai-Sheng et al. 2008), but their activities are largely limited by electron acceptor availability. Current research has indicated that both oxygen and nitrate addition are capable of enhancing in situ bioremediation, and the objective of this laboratory experiment was to stimulate aerobic PAH degradation in contaminated sediment through the addition of either solid oxygen release compounds (ORC®) or potassium nitrate crystals. Phenanthrene biodegradation in laboratory-contaminated sediment by aerobic microbes was significantly enhanced through solid magnesium peroxide cube (ORC ®) addition to both low organic content (LOC) and high organic content (HOC) sediments, eventually reaching 70% removal in LOC sediments and 51% in HOC sediments. Waters overlying LOC sediments were supersaturated with oxygen, with dissolved oxygen (DO) levels reaching 13.6 mg/L, while waters overlying HOC sediments maintained relatively low DO levels. pH in overlying waters was not significantly influenced in LOC sediments and slight, but still insignificant, increases were observed in HOC sediment microcosms. Nitrate treatment was only examined in HOC sediments and failed to enhance phenanthrene remediation. DO levels were significantly raised, possibly due to microbial inhibition, and pH remained constant. PCR analysis of sediment samples for dioxygenase presence confirmed the existence of PAH degraders in both oxygen amended and control microcosms. ORC® treated samples also showed increasing PAH degrader presence over time, which corresponded to observed increases in phenanthrene degradation. Despite high DO levels in nitrate treated microcosms, dioxygenase levels suggested that PAH degrading populations did not grow throughout the course of the experiment. These data showed high potential for solid peroxide-stimulated biodegradation as a sediment remediation technique, and warrant further research both in the laboratory and in the field. Conversely, nitrate did not appear to be an effective remediation tool for the soils tested, and was even suspected to have inhibited microbial activity.

Solid peroxide stimulated phenanthrene removal from contaminated river sediment

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